Mechanistic aspects of electrochemical corrosion of aluminum alloy in ethylene glycol–water solution

The electrochemical corrosion behavior of 3003 aluminum (Al) alloy in ethylene glycol–water solutions was studied by electrochemical measurements and surface analysis techniques through an impingement jet system. Al corrosion in aerated, stationary solution is a mixed-controlled process, i.e., both activation and mass-transfer steps control the corrosion reaction. Upon flowing of solution, no matter if sand particles are contained, Al corrosion is an activation-controlled process. In addition to Al oxide film, a layer of Al-alcohol film will also be formed on the electrode surface in ethylene glycol–water solution, contributing to inhibition of anodic dissolution of Al. In the absence of oxygen, a stable passivity could also be achieved on Al alloy. The main cathodic reaction is either reduction of water or reduction of ethylene glycol. However, the reduction of water and ethylene glycol would not be as significant as that of oxygen. As a consequence, the resultant film is not as stable as that formed in the presence of oxygen, as shown in polarization measurements. Al corrosion reaction in mixed-controlled by activation step and mass-transfer step through the anodic surface film. The coverage of the adsorbed intermediate product on Al electrode surface is expected to be very small under the impingement of fluid and sand particles, which results in the generation of an inductive loop in Nyquist diagrams measured on Al electrode in ethylene glycol–water solution.